1. Field of the Invention
The present invention relates to a semiconductor device which is so constructed that a power IC, an ECL gate array, a large scale CMOS gate array or the like is mounted on a semiconductor mounting section using a semiconductor mounting plate.
2. Description of the Related Art
In a conventional semiconductor device, as shown in FIGS. 1A and 1B, a semiconductor chip 11 on which various functional and passive devices are mounted is directly connected to a radiating plate 12-1 by a conductive adhesive 13 such as solder and paste. The radiating plate 12-1 is attached to the back of a semiconductor chip mounting section 12 so as to cover a through hole 14 formed in the semiconductor chip mounting section 12.
The purpose of directly connecting the semiconductor chip 11 to the radiating plate 12-1 is to improve in radiation characteristics.
Since the back of the semiconductor chip 11 is connected to the radiating plate 12-1, the semiconductor chip is connected to a GND pin 15 formed on the semiconductor chip mounting section 12 through a wire 14-1. A wire 14-2 is used to connect the semiconductor chip 11 to a terminal pin 15-2.
The back of the radiating plate 12-1 is generally used as a ground side. Since, however, the semiconductor chip 11 is not electrically separated from the radiating plate 12-1, the semiconductor chip 11, the radiating plate 12-1, and the GND pin 15-1 are set to the same potential when a voltage is applied to the semiconductor chip 11. Therefore, the radiating plate 12-1 has a predetermined potential with its back exposed to open air.
Further, since the semiconductor chip 11 is not electrically independent of the radiating plate 12-1, it cannot receive its proper voltage from the back thereof.
For example, if wind is given to the semiconductor chip 11 when the semiconductor device is cooled, an electrostatic potential occurs in the radiating plate 12-1, with the result that the GND potential causes a so-called fluctuation phenomenon.